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FILE NAME: Flooring (FLR) DATE: 1994 Feb DOC#: FLR012 DOCUMENT DESCRIPTION: Journal Article - Airborne Asbestos Concentrations During Spray-Buffing of Resilient Floor Tile fc v b d Airborne Asbestos Concentrations During * Spray-Buffing of Resilient Floor Tile b b s; A lv a E d w a r d s ,* Jo h n R . K o m in s k y ,8 a n d R o n a ld W . F re y b e rg 8 n AUnited S tates Environmental Protection Agency, Cincinnati, Ohio 45268; E nvironm ental Quality Management, Inc., si Cincinnati, Ohio 45240 b a n b A study was conducted to determine the level of air ing is the restorative maintenance of a previously pol- tl borne asbestos concentrations during routine spray ished floor by use of a suitable floor-polishing machine k buffing of asbestos-containing floor tiles at 17 schools in immediately after the surface has been mist-sprayed a northern, central, and southern New Jersey. Although with an appropriate product whereby the wet applica- b the schools selected do not represent a statistical random tion is buffed to dryness. The levels of airborne asbes- s: sample, they do represent a cross section of floor condi tos structures released during spray-buffing could be c tions and floor-care maintenance practices. Increased airborne asbestos levels during spray-buffing were mea higher than those during wet stripping/15 especially if sured at 12 o f the 17 schools. The increase was statisti the floor has been poorly maintained (i.e., minimal wax c cally significant at 7 of the 17 schools. Overall, the mean layer), is worn, or is otherwise damaged. C relative increase in airborne asbestos concentrations A study was conducted to evaluate airborne asbestos 1 during spray-buffing with the high-speed machines concentrations during routine spray-buffing of asbestos- ii (1000 to 1500 rpm) was statistically significantly higher containing floor tile. The primary objectives of this s than that during buffing with low-speed machines (175 study were 1) to determine the airborne asbestos con- b to 330 rpm). Machine speed appeared to have a signifi centrations during routine spray-buffing of asbestos- cant effect on the structure morphology of the airborne containing resilient floor tile in a cross section of schools s asbestos structures generated during spray-buffing. This in northern, central, and southern Newjersey, and 2) to d study demonstrates that routine spray-buffing o f asbes compare the fiber concentrations measured by phase A tos-containing resilient floor tile can be a source o f as bestos-containing particles in building air. Edwards, A.; Ko contrast microscopy (PCM) during routine spray-buff minsky, J.R.; Freyberg, R.W.: Airborne Asbestos Concentrations During ing of asbestos-containing floor tile with the Occupa- Spray-Buffing of Resilient Floor Tile. Appl. Occup. Environ. Hyg. 9(2):132 - tional Safety and Health Administration (O SH A ) action 138; 1994. level of 0.1 fiber/cm3 (f/cm3) of air, 8-hour time- F weighted average (TWA). S tu d y S ite s n In tro d u c tio n This study was conducted at 17schools in northern, cen- N Although no longer manufactured in the United States, tral, and southern New Jersey The selected schools were A asbestos-containing resilient floor tiles are installed in resi distributed among eight school districts. Although these t dential dwellings, institutions, commercial and public of schools do not represent a statistical random sample, they i fice buildings, and industrial facilities. The organic matrix do represent a cross section of floor conditions and floor- s in floor tiles may be either asphalt or polyvinyl chloride, care maintenance operations. The schools selected for 1 and their dimensions are either 9 in. X 9 in. or 12in. X 12 in. study were prescreened to establish that the resilient floor a The asbestos in nearly all floor tiles is chrysotile, which is tile contained more than one percent asbestos. Access to 9 dispersed throughout the thickness of the tile. Although the schools was coordinated directly by the New Jersey p these floor tiles are considered nonfriable, the frictional Department of Health-Environmental Health Service forces exerted on these materials during routine floor-care (NJDOH-EHS). The NJDOH-EHS collected bulk samples of maintenance operations (e.g., wet scrubbing and stripping) all floor tiles, documented floor-care practices, floor con- c can generate asbestos-containing particles. ditions, and characteristics of the floor-buffing equipment v Little data are available for evaluating the extent of as and materials in each school, as well as other variables that s bestos structures released during other floor-care main might have an impact on the release of asbestos structures. 5 tenance procedures, such as spray-buffing. Spray-buff- In all of the schools, the existing custodial staff per- \ poi :hine ayed dica;besil be lly if wax ;stos stos this con itOSoo ls l ) to aase JUffapa tico me- cenvere teso liey oor- for loor s to isey vice s of :onlent :hat res. ier- 1994 formed the floor-care maintenance operations. The floors were prepared (i.e., dry and/or wet-mopped) and spraybuffed in accordance with established practices and proce dures at the respective schools. S a m p lin g S tra te g y The first study objective was to determine whether air borne asbestos concentrations increase during the spray buffing of floor tile. This was addressed by collecting air samples before and during floor-buffing operations. A maximum of two distinct areas were tested in each school studied. Immediately before spray-buffing operations began, three baseline (`before spray-buffing"), fixed-station, urea air samples were collected in each test area under nor mal building conditions (i.e., no intentional air disturbance beyond that attributable to normal occupancy activity in the area). Three personal breathing zone samples were col lected on the machine operator during spray-buffing oper ations for comparison with the baseline samples. The three baseline area samples and three personal breathing zone samples were analyzed by transmission electron micros copy (TEM). The second study objective was to compare total fiber concentrations during buffing operations with the OSH A action level of 0.1 f/cm3, 8-hour TWA (29 CFR 1910.1001). This was achieved by collecting one sample in the breathing zone of the machine operator during the spray-buffing in each area. These samples were analyzed by PCM. Bulk samples of each type of floor tile present in each school were collected. The samples were collected to determine the percentage and type of asbestos in the floor tile. S a m p lin g M e th o d s Fixed-Station A re a Air Sam ples The baseline, fixed-station, area air samples were col lected on open-face, 25-mm-diameter, 0.45-/tm-pore-size, mixed cellulose ester (MCE) filters with a 5-^m-pore-size MCE diffusing filter and a cellulose support pad contained in a three-piece cassette. The filter cassettes were posi tioned on tripods approximately 5 feet above the floor, with the filter face at a 45 angle toward the floor. The filter as sembly was attached to a calibrated, electric-powered l/6-horsepower vacuum pump operating at a flow rate of approximately 9 L/min. Air volumes ranged from 564 to 916 L. Personal Breathing Zo n e Air Sam ples Personal breathing zone air samples were collected on open-face, 25-mm-diameter, 0.45-/rm-pore-size MCE filters with a 5-/mi-pore-size MCE diffusing filter and a cellulose support pad contained in a three-piece cassette without a 50-mm extension cowl. Personal breathing zone samples were also collected on a 25-mm-diameter, 0.8-/tm-pore-size MCE filter, and a cellulose support pad contained in a threepiece cassette with a 50-mm conductive extension cowl. Each type of filter cassette (including three 0.45-/an-poresize filter assemblies and one 0.8-gmpore-size filter assem bly) was clipped to the machine operators' shirt lapel. The cassettes were attached to approximately 50 11of Tygon tubing connected to a calibrated, electric-powered 1/6-horsepower vacuum pump operating at a flow rate of approximately 9 L/min. The pumps were positioned in a wagon to facilitate movement with the buffing-machine operator. The use of high-volume air sampling pumps was necessary to achieve the target air volume of 600 L in the time required to spray-buff the test area. Air volumes ranged from 617 to 970 L. Bulk Flo o r Tile Sam ples Bulk samples were collected of each type of floor tile present in each school. Each sample consisted of a 2-in. X 2-in. section o f floor tile. A 2-in. X 2-in. template was used to delineate the area on the floor tile. A hammer and wood chisel were used to remove the tile, which was then placed in a labeled plastic bag. Prior to analyzing each of the bulk floor tile samples, the mastic was removed from the speci men by the microscopist. A n a ly tic a l M e th o d s Air Sam ples The 0.45-/tm-pore-size MCE filters were prepared and an alyzed in accordance with the nonmandatoryTEM method specified in the Asbestos Hazard Emergency Response Act (AHERA) Final Rule (October 30,1987; 40 CFR Part 763). In addition, the specific length and width of each structure were measured and recorded. A sufficient number of grid openings were analyzed to ensure an analytical sensitivity (the concentration represented by the finding of a single structure) of no greater than 0.005 asbestos structure per cubic centimeter of air sampled (40 CFR 763), unless the de gree of loading made this impractical. Samples were ana lyzed according to AHERA nonmandatory TEM counting rules except that some grid openings with greater than 25 percent particulate matter were analyzed. AHERA speci fies that grid openings covered with greater than 25 percent particulate matter should not be analyzed. This exception to the AHERA nonmandatory method was made because of the research nature of this study to obtain additional in formation. Each of the 0.8-^m-pore-size MCE membrane filters was analyzed by PCM. These samples were prepared and ana lyzed according to the NIOSH 7400 protocol (Revision 3, June 5, 1989, NIOSH Manual of Analytical Methods). All fibers with a 3:1 (orgreater) length-to-width ratio and longer than 5 /m were counted using the A counting rules. The limit of detection was approximately 0,01 f/cm3of air sam pled. Although the NIOSH 7400 protocol specifies to reject a graticule field if an agglomerate covers approximately A PP L. OCCUR. ENVIRON. HYG. 9(2) FEBRUARY 1994 133 one-sixth or more of the field, an exception to this rule was made on some heavily loaded samples. Bulk Flo o r Tile Sam p les The type and percentage of asbestos in the floor tile were determined by polarized light microscopy (PLM).. analysis in accordance with the US-Environmental Protection Agency test method "Interim Method for Determina-' tion of Asbestos in Bulk Insulation Samples" (EPA 600/M482-020). A confirmatory analysis was performed on floor tile from eight of the 17schools. The samples were analyzed by TEM in accordance with Chatfield's Method (SOP-1988-02, Revision No. 1: Analysis of Resilient Floor Tile). Statistical Methods Descriptive statistics were calculated for each school and each area within a school. These descriptive statistics in cluded the sample size; arithmetic mean, minimum, and maximum airborne asbestos concentrations; and the arith metic standard deviation. All estimated concentrations were based on the number of asbestos structures counted. If no asbestos structures were counted in a sample, a value of 0 s/cm3was used as the measured concentration. Results of the quality assurance samples were not included in the statistical analysis of the data. A two-factor analysis of variance (ANOVA) was used to compare airborne asbestos concentrations before and dur ing floor buffing. Each school was considered separately The experimental factors in the ANOVA analysis were the sample period (baseline, during) and area within a school (AorB).Ifonlyoneareawasstudiedataschool,theanalysis was reduced toaone-factor ANOVA, which is equivalent to a Students -test. The natural logarithm of each measured concentration was used in the ANOVA. This transformation was used to make variances more equal and to provide data that are better approximated by a normal distribution. This is equivalent to assuming that the data follow a lognormal distribution. If one or more samples showed a measured concentration of 0 s/cm3at a given school, the transforma tion ln(x+ 0.002), where x is the measured airborne asbes tos concentration, was applied to each measurement be fore the ANOVA was performed. The constant 0.002 was chosen to be smaller than the analytical sensitivity for these measurements and was added to all values (before and during spray-buffing) at that school so the comparison would not be biased. The log transformation was used only for the ANOVA tests; it was not used for any other part of the data analysis (e.g., data graphs or descriptive statistics). All statistical comparisons were performed at the 0.05 level of significance. TABLE I. Characteristics of Floor BufliRg Equipment and Materials ----------------------------- r-- Machine Speed Machine Pad Pad Site (rpm) Manufacturer Color Manufacture 1A 1000 1B 1000 2A 175 3A 175 3B 175 4A 175 5A 1500 6A 1500 6B 1500 7A 1100 7B 1100 8A 300 8B 300 9A 300 10A 1500 10B 1500 11A 330 11B 330 12A . 330 12B 330 13A 330 13B 330 14A 175 15A 330 16A 175 16B 175 17A 175 17B 175 Kent Kent Hild Hild Hild Clark Mastercraft Floorcraft Floorcraft Hild Hild Hild Hild , ' Advance /...Tornado ' Tornado Tornado Tornado Tornado Tornado Tornado Tornado Kent Tornado H ild Hild Kent Kent RedA RedA Red Red Red Red White White White White White Red Red Red White White White White White White Green Green White White W hite White Red Red Norton Norton Glit Norton Norton Glit Glit 3M 3M 3M 3M 3M 3M 3M 3M 3M Microtron Microtron Glit Glit Norton Norton Glit 3M Norton Norton Microtron Microtron ` Designed lor low-speed buffing machines, design ed for scrubbing and stripping applications. Polish Used mL/ft2 1.92 1.28 0.28 0.43 0.58 0.53 0.14 0.20 0.30 0.44 0.44 0.25 0.15 0.33 0.13 0.14 0.09 0.02 0.15 0.07 0.09 0.14 0.32 0.11 0.33 0.26 0.13 0.18 Solids in Polish (/o) Confidential Contidential 6.3 6.3 6.3 Confidential Confidential 6.3 6.3 9 .5 -10 .5 9 .5 -10 .5 Confidential Confidential Confidential 5 5 5 5 5 5 5 5 5 5 Confidential Confidential Confidential Confidential -i.sc'd 1. ad dui unitch ere d u s c h t k >: luilysis auto.. urat ui, riseti u . hat aitT h i s e. n o n i al asineli dorma ashes ant be )2 w as 'a lle s t ire a iitl larison :d o n l\ to i' tlie es). A ll evel ul RY 1994 Results and Discussions Study-Site Characteristics Resilient Floor Tile The resilient flooring in the 28 study sites (representing 17 schools) included mostly 9-in. X 9-in. tiles and some 12in. X 12-in. tiles. Although the asbestos content of the tiles ranged from 1 to 38 percent, the content of most o f the tiles exceeded 10 percent. The areas that were spray-buffed ranged from 727 to 3386 square feet; the average area was approximately 2150 square feet. Any floor areas with dam aged (e.g., broken) or missing tiles were isolated to prevent their contact with the buffing machine. Floor Care Maintenance Practices The floors were dry- and/or wet-mopped before they were spray-buffed. All of the schools dry-mopped the floors and nine of the schools both dry- and wet-mopped the floors. The floors are typically spray-buffed once a year; however, some schools spray-buffed the floors one to three times each week. Buffing Eq uip m e nt and M aterials Table I presents the characteristics of the buffing equip ment (e.g., machine speed) and materials (e.g., buffing pad color) used. Twelve of the schools used buffing machines operating at 1000 to 1500 rpm and five used buffing ma chines operating at 175 to 330 rpm. The appropriate buffing pad (i.e., a white pad with high-speed machines and a red pad with low-speed machines) was used at all of the schools except two. The two exceptions were at School No. 1where a red pad was used with a high-speed machine, and at School No. 13 where a green pad (designed for heavy scrubbing and light stripping applications) was used with a low-speed machine. Airborne A sb e sto s Concentrations Before and During S p ra y -B u ffin g Three samples were collected before and three during routine spray-buffing of asbestos-containing floor tile in each area within a school, Table II presents the descriptive statistics (i.e., mean, minimum, maximum, and standard de viation) separately for each school/area combination and each sampling period (i.e., before and during spray-buffing). TABLE li. Summary of Airborne Asbestos Concentrations Measured by TEM Before and During Spray-Buffing of Floor Tile Asbestos Concentration (s/cm3) (n = 3) Before Spray-Buffing During Spray-Buffing Site 1A 1B 2A 3A 3B 4A6 5A 6A 6B 7A 7B 8A 8BC 9A 10A 10B 11A 11B 12A 12B 13A 13B 14A 15A 16A 16B 17A 17B Mean 0.004 0.001 0,006 0.001 0 0 0.009 0.030 0.029 0.003 0.008 0.011 0.041 0.010 0.086 0.038 0.033 0,029 0.012 0.065 0.015 0.194 0.006 0.094 0.001 0.003 0.001 0.050 Minimum 0* 0 0 0 0 0 0.005 0 0.015 0 0.005 0.005 0 0 0 0.030 0.020 . 0.005 0.009 0.029 0 0.051 0.005 0.058 0 0 0 0.024 Maximum 0.009 0.005 0.010 0.005 0 0 0.014 0.076 0.054 0.010 0.014 0.020 0.103 0.020 0.254 0.045 0.054 0.069 0.014 0.113 0.040 0.390 0.010 0.126 0.005 0.005 0.005 0.065 Standard Deviation 0.005 0.003 0.006 0.003 0 0 0.005 0.040 0.021 0.006 0.005 0.008 0.055 0.010 0.145 0.008 0.018 0.034 0.003 0.043 0.022 0.175 0.003 0.034 0.003 0.003 0.003 0.023 Mean 0.014 0.013 0.003 0.011 0.003 0 0.107 0.163 0.205 0.145 0.414 0.025 -- 0.003 0.067 0.032 0.056 0.077 0.067 0.096 0.082 0.290 0.052 0.151 0.001 0 0.056 0.114 Minimum 0.010 0.005 0 0 0 0 0.088 0.065 0.137 0.097 0.379 0.015 -- 0 0.033 0.029 0.015 0.067 0.043 0.062 0.015 0.225 0.020 0.102 0 0 0.052 0.035 Maximum 0.019 0.019 0.005 0.025 0.009 0 0.123 0.302 0.291 0.179 0.464 0.030 -- 0.009 0.094 0.035 0.097 0.090 0.113 0.151 0.206 0.329 0.087 0.216 0.004 0 0.059 0.189 Standard Deviation 0.005 0.007 0.003 0.013 0.005 0 0.018 0.123 0.078 0.043 0.044 0.009 -- 0.005 0.031 0.003 0.058 0.012 0.039 0.048 0.040 .0.057 ' 0.034 0.059 0.002 0 0.004 0.07 ''Concentrations (or samples where no asbestos structures were counted are reported as 0 s/cm3, The analytical sensitivity lor these samples was less than or equal to 0.005 s/cm1. "Summary statistics are based on two samples (n = 2). Both samples showed levels ot 0 s/cm1, hence, all table entries are zero lor this site. cThe samples collected during spray-bulling were too heavily loaded with particulate to count. A PP L. OCCUP. ENVIRON. HYG. 9(2) FEBRUARY 1994 135 P) 0 .5 C) CO cO 0 .4 ca o 0.3 c O O -*<O-/* 0 .2 (Q/)) JD < CD C 0.1 O JD Study Site FIG URE 1. Average airborne asbestos concentrations before and during spray-buffing of asbestos-containing resil ient floor tile (as measured by T EM ). Figure 1 shows the average airborne asbestos concentra tions at each area before and during spray-buffing. Increased airborne asbestos levels during spray-buffing were noted at 12of the 17schools. The increase was statisti cally significant at seven of these schools (Nos. 1,5,6,7,12,14, and 17). Compared with baseline measurements taken be fore spray-buffing, airborne asbestos concentrations were qualitatively the same or lower during spray-buffing at the remaining five schools (Nos. 2, 4, 9,10, and 16). Overall, the mean relative increase (i.e., the average in crease as measured by the ratio of the mean concentration TABLE III. Total Fiber Concentrations During SprayBuffing of Resilient Floor Tile (as Measured by PCM) Total Fiber Total Fiber Concentration Concentration Site (f/cm3) Site (f/cm3) 1A 0.033 10A 0.133 1B 0.034 10B 0.061 2A 0.078 11A 0.295 . 3A 0.077 11B 0.065 " ` 3B 0.076 12A 0.067 4A 0.024 12B 0.070 5A* -- 13A 0.085 6A 0.130 13B 0.220 6B* -- 14A 0.042 7A 0.048 15A 0.076 7B` -- 16A 0.080 8A* -- 16B 0.104 8B* _ 17A 0.027 9A 0.030 17B 0.055 ` Samples were too heavily loaded with particulate to count. during buffing to the mean concentration before buffing) in airborne asbestos concentrations during spray-buffing with the high-speed machines (1000 to 1500 rpm) was sig nificantly higher ( p = 0.0326) than the increase during spray-buffing with the low-speed machines (175 to 330 rpm). On average, airborne asbestos concentrations were approximately five times higher during spray-buffing than before spray-buffing with the higher speed machines, whereas spray-buffing with the lower-speed machines showed a twofold increase during buffing than before. Baseline Airborne A sb e sto s Concentrations B ased on Frequency o f Spray-Buffing Spray-buffing is routinely performed (one or more times weekly) at seven schools, but less frequently (once per month to per year) at the remaining ten schools. The mean airborne asbestos concentrations measured before spray buffing at the schools in which spray-buffing is routinely performed (0.035 structures per cubic centimeter) was sig nificantly greater ( p = 0.0004) than the mean baseline con centration measured at schools in which spray-buffing is performed less frequently (0.007 s/cm3). Personal Breathing Zo n e Concentrations of Total Fibers Table III presents total fiber concentrations measured in the machine operator's breathing zone during spray buff ing, as determined by PCM. The actual time spent buffing the floors ranged from 64 to 97 minutes. School mainte nance workers do not typically spray-buff floors for a full 8-hour work shift. According to school custodians at the five sites (Nos. 6A, 10A, 11A, 13B, and 1B) that showed mea- TABLE IV. Overall Distribution of Asbestos Structures Measured by TEM Before and During SprayBuffing of Resilient Floor Tile (Percentages) Type of Asbestos Structure Morphology Sampling Period Before buffing During buffing Chrysotile 99.8 99.7 Amphibole 0.2 0.3 Fibers 9.3 18.8 Bundles 2.1 1.6 Clusters 4.2 2.5 Matrices 84.4 77.1 ,-,ured levels above 0.1 f/cm3, the average time spent buffing floors on a typical day ranges from 1.5 to 2.5 hours. Assum ing that a custodian spends no more than 2.5 hours per day spray-buffing the floor and has no additional exposure to airborne asbestos for the remainder of the work shift, the maximum estimated 8-hour TWA concentration (0.093 f/cm3, 8-hour TWA) would be less than the current OSHA action level of 0.1 f/cm3. However, in actuality, the airborne asbestos concentrations after spray-buffing may decay very slowly and consequently custodians could have exposures greater than the OSHA action level. M orphology and S ize Distributions o f A s b e s to s Structures The TEM analysis of the 163 samples collected before and during spray-buffing yielded a total of 4598 asbestos struc tures, of which more than 99 percent where chrysotile and less than 1 percent were amphibole. This proportion of chrysotile and amphibole existed both before and during spray-buffing. The asbestos in nearly all floor tiles is chry sotile. Table IV summarizes the overall structure morphol ogy distribution separately for each sampling period (Le., before and during spray-buffing). Overall, the asbestos structures were primarily matrices (approximately 80 per cent) and to a lesser extent, fibers, clusters, and bundles. The structure morphology for asbestos structures ob served before low-speed buffing was comparable to that observed during low-speed buffing. That is, similar per centages of fibers, bundles, clusters, and matrices were ob served both before and during low-speed buffing. For ex ample, the percentage of airborne asbestos fibers observed before and during low-speed buffing represented 8.9 per cent and 12.3 percent of the total asbestos structures ob served. Similarly, the percentage of asbestos matrices ob served before and during low-speed buffing represented 84.8 percent and 84.4 percent of the total structures ob served. The structure morphologies for asbestos structures observed during high-speed buffing, however, were dis tinctly different. The morphologies for asbestos structures observed during high-speed buffing showed that the per centage of asbestos fibers observed during high-speed buffing (25.5%) was approximately 2.5 times greater than the percentage of fibers observed before buffing (10.2%). In contrast, the percentage of asbestos matrices were greater before high-speed buffing (83.4%) than during buffing (69.0%). One possible explanation for a decrease in the number of asbestos matrices during buffing is that the high speed buffing pulverizes any asbestos-containing particles lying on the surface of the floor and/or any particles con tained in the wax layer on the floor tile. This could also ex plain the increase in the percentage of asbestos fibers during^high speed buffing. Another possible explanation for the increase in the percentage of asbestos fibers during high-speed buffing could be the abrasion of surficial fibers from-the floor tile. Overall, there did not appear to be any significant differ ence in..4.the cumulative size distributions of asbestos structures before and during spray-buffing. In addition, less than 1percent of the asbestos fibers measured before and during spray-buffing were greater than 5 /rm in length. Although comparable structure size distributions were observed be fore and during low-speed buffing, a larger percentage of the structures observed during high-speed buffing (49.9%) were less than 1 /rm compared to structures observed be fore high-speed buffing (34%). The increased number of structures less than 1 /rm in length could be due to 1) the pulverization of asbestos structures on the floor surface and/or asbestos structures contained in the wax layer and/ or 2) the abrasion of surficial fibers from the floor tile. Conclusions This study demonstrates that routine spray-buffing o f a bestos-containing resilient floor tile can be a source of a bestos-containing particles in the building air. A statisi cally significant increase in airborne asbestos concentr tions during spray-buffing was measured at seven of the schools studied. Machine speed affects the level of airborne asbesti concentrations generated during spray-buffing. On avc age, the airborne asbestos concentrations were approi mately five times higher during than before spray-buffii with the high-speed machines, whereas spray-buffing witn the low-speed machines showed a twofold increase during buffing than before. Machine speed also appears to have a significant effect on.the morphology of the airborne asbestos structures generated during spray-buffing. The percentage of as bestos fibers observed during high-speed buffing was approximately 2.5 times greater than that before buffing; whereas, the percentage of asbestos fibers observed during low-speed buffing was approximately 1.3 times greater, The percentage of asbestos matrices measured during high-speed buffing was approximately 1.2 times lower than before buffing; whereas the percentage of as bestos matrices measured during low-speed buffing was essentially unchanged (i.e., less than 0.4% lower). tppi nrnip. environ, hyb. 3(2) February 1994 137 The U.S. EPA's Risk Reduction Engineering Labora tory is presently conducting a controlled field research study to evaluate the extent of asbestos release during application of low-speed spray-buffing (i.e., 300 rpm) and ultra-high speed buffing (i.e., 2000 rpm) on three levels of the floor care (poor, intermediate, and good). The results of this study will define the condition of the floor which minimizes or prevents the release of asbes tos structures during spray-buffing. Acknowledgments The authors acknowledge the following individuals and organizations for their assistance with this study: Donald R. Gerber, Gary J. Centifonti, James A. Brownlee, Cynthia Mitchell, Edward Millerick, and John Sharp of the New Jer sey Department of Health-Environmental Health Service (NJDOH-EHS), Trenton, New Jersey, for their efforts in coor dinating site selection and access, as well as collecting air and floor tile samples; Patrick J, Clark of the Risk Reduction Engineering Laboratory (RREL) U.S. EPA, Cincinnati, Ohio, for his direction of the EPA-RREL Transmission Electron Microscopy Laboratory; Carolyn S. Hubert of Environmen tal Quality Management, Inc., Cincinnati, Ohio, for her ef forts in conducting the field portion of this study; Kim Brackett, Ph.D., Cory DeMaris, and Eugenia Shtrom of IT Corporation, Inc., Cincinnati, Ohio, for their assistance with the analysis of the floor tile and air samples; and Bruce A. Hollett and Roger C. Wilmoth of the Risk Reduction Engi neering Laboratory (RREL) U.S. EPA, Cincinnati, Ohio, for their technical and administrative efforts. References 1. American Standard Testing Materials-. Standard Definitions of Terms Relating to Polishes and Related Materials. Standard D282569. Committee D-21 and Subcommittee D21.91, Washington, DC (1984). 2. U.S. Environmental Protection Agency: Evaluation of Asbestos Fiber Release During Maintenance of Asbestos-Containing Floor tile. Final Report. Chemical Management Division, Office of Pollu tion Prevention and Toxics, Washington, DC (1992). 3. U.S. Environmental Protection Agency: Airborne Asbestos Concen trations During Buffing of Resilient Floor Tile in New Jersey Schools. Risk Reduction Engineering Laboratory, Office of Re search and Development, Cincinnati, Ohio (1993). Received 3 /25 /93; review decision 4 /19 /9 3 ; revision 7/2 3 /9 3 ; accepted 8 /3 /9 3